docs: def index():
      """List the available crawlers."""
      crawler_list = []
      for crawler in manager:
          is_due = 'yes' if crawler.check_due() else 'no'
          if crawler.disabled:
              is_due = 'off'
          crawler_list.append([crawler.name,
                               crawler.description,
                               crawler.schedule,
                               is_due,
                               Queue.size(crawler)])
      headers = ['Name', 'Description', 'Schedule', 'Due', 'Pending']
      print(tabulate(crawler_list, headers=headers))